1. Field of the Invention
The present invention relates to a prism lens sheet capable of optically controlling the luminance and the viewing angle of a screen, and a backlight system employing such a prism lens sheet for use in a liquid crystal display.
2. Description of the Related Art
Lightweight, high-definition liquid crystal displays have been developed and have widely been applied to office automation machines including personal computers. A liquid crystal display is provided with a backlight system to enable its screen to secure a proper luminance or brightness because liquid crystal itself does not emit light. Personal computers of a notebook type have come into wide use recently. Such personal computers provided with a liquid crystal display have become often used personally in an open space, and it is desired that the liquid crystal display has a relatively small viewing angle in view of protecting information displayed on the screen of the liquid crystal display. Therefore, it is desirable to control the brightness and the viewing angle of the screen of the liquid crystal display by an improved backlight system. Such a requirement may be met by enhancing the brightness of the backlight system to increase the directivity of light emitted from the backlight system toward the viewer. However, the increase in the brightness of the backlight system entails increase in power consumption, heat generation and costs.